The present invention relates to an optical fiber sensor in which a plastic fiber for detection is inserted in an insertion hole of a molded member, a manufacturing method thereof, and a collision detection device for a vehicle in which the optical fiber sensor is used as a collision detection sensor.
In FS sensor (flexible pressure sensitive sensor) widely used as an electric load sensor (or, an impact detection sensor), a conductor for detection is inserted in a hole of a rubber tube. When the conductor is inserted in the hole of the rubber tube at manufacturing FS sensor, a compressed air is sent to the hole of the rubber tube, the size of which is smaller than outside diameter of the conductor, and the rubber tube be swollen. When the compressed air is evacuated after the conductor is inserted in the hole of the rubber tube under such a condition, the rubber tube shrinks and a gap between the rubber tube and the conductor disappears almost.
With regard to FS sensor, the rubber tube swells evenly when the compressed air is sent to the hole of the rubber tube because wall thickness of the rubber tube is thick and uniform. However, if the wall thickness of the rubber tube is not uniform, a thin part swells intensively, and it is likely to rupture at the end.
Because FS sensor is weak to electric noises and electromagnetic noises, an optical fiber sensor has come to be used instead of FS sensor, which has the same function as FS sensor and is very strong to electric noises and electromagnetic noises.
In a conventional optical fiber sensor, a stress-concentration plate with press punched holes is molded with a molded member, and a plastic fiber (POF) for detection is inserted in an insertion hole of the molded member.
In a method of manufacturing an optical fiber sensor, the compressed air is sent to the insertion hole of the molded member, and the POF is inserted in the insertion hole in its state, as is the case with the manufacturing method of FS sensor.
Such a conventional technique is disclosed, for example, in PCT international publication No. WO 00/32449.